[PATCH v8 02/24] scripts/jobserver-exec: move its class to the lib directory

Mauro Carvalho Chehab
2025-09-18T11:55:06Z

To make it easier to be re-used, move the JobserverExec class
to the library directory.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
scripts/jobserver-exec | 152 +++------------------------------------
scripts/lib/jobserver.py | 149 ++++++++++++++++++++++++++++++++++++++
2 files changed, 160 insertions(+), 141 deletions(-)
create mode 100755 scripts/lib/jobserver.py

diff --git a/scripts/jobserver-exec b/scripts/jobserver-exec
index 897c0cca9e6e..40a0f0058733 100755
--- a/scripts/jobserver-exec
+++ b/scripts/jobserver-exec
@@ -1,155 +1,25 @@
#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0+
-#
-# pylint: disable=C0103,C0209
-#
-# This determines how many parallel tasks "make" is expecting, as it is
-# not exposed via an special variables, reserves them all, runs a subprocess
-# with PARALLELISM environment variable set, and releases the jobs back again.
-#
-# https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver

-"""
-Interacts with the POSIX jobserver during the Kernel build time.
-
-A "normal" jobserver task, like the one initiated by a make subrocess would do:
-
- - open read/write file descriptors to communicate with the job server;
- - ask for one slot by calling:
- claim = os.read(reader, 1)
- - when the job finshes, call:
- os.write(writer, b"+") # os.write(writer, claim)
-
-Here, the goal is different: This script aims to get the remaining number
-of slots available, using all of them to run a command which handle tasks in
-parallel. To to that, it has a loop that ends only after there are no
-slots left. It then increments the number by one, in order to allow a
-call equivalent to make -j$((claim+1)), e.g. having a parent make creating
-$claim child to do the actual work.
-
-The end goal here is to keep the total number of build tasks under the
-limit established by the initial make -j$n_proc call.
-"""
-
-import errno
import os
-import subprocess
import sys

+LIB_DIR = "lib"
+SRC_DIR = os.path.dirname(os.path.realpath(__file__))

-class JobserverExec:
- """
- Claim all slots from make using POSIX Jobserver.
+sys.path.insert(0, os.path.join(SRC_DIR, LIB_DIR))

- The main methods here are:
- - open(): reserves all slots;
- - close(): method returns all used slots back to make;
- - run(): executes a command setting PARALLELISM=<available slots jobs + 1>
- """
+from jobserver import JobserverExec # pylint: disable=C0415

- def __init__(self):
- """Initialize internal vars"""
- self.claim = 0
- self.jobs = b""
- self.reader = None
- self.writer = None
- self.is_open = False

- def open(self):
- """Reserve all available slots to be claimed later on"""
-
- if self.is_open:
- return
-
- try:
- # Fetch the make environment options.
- flags = os.environ["MAKEFLAGS"]
- # Look for "--jobserver=R,W"
- # Note that GNU Make has used --jobserver-fds and --jobserver-auth
- # so this handles all of them.
- opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
-
- # Parse out R,W file descriptor numbers and set them nonblocking.
- # If the MAKEFLAGS variable contains multiple instances of the
- # --jobserver-auth= option, the last one is relevant.
- fds = opts[-1].split("=", 1)[1]
-
- # Starting with GNU Make 4.4, named pipes are used for reader
- # and writer.
- # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134
- _, _, path = fds.partition("fifo:")
-
- if path:
- self.reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
- self.writer = os.open(path, os.O_WRONLY)
- else:
- self.reader, self.writer = [int(x) for x in fds.split(",", 1)]
- # Open a private copy of reader to avoid setting nonblocking
- # on an unexpecting process with the same reader fd.
- self.reader = os.open("/proc/self/fd/%d" % (self.reader),
- os.O_RDONLY | os.O_NONBLOCK)
-
- # Read out as many jobserver slots as possible
- while True:
- try:
- slot = os.read(self.reader, 8)
- self.jobs += slot
- except (OSError, IOError) as e:
- if e.errno == errno.EWOULDBLOCK:
- # Stop at the end of the jobserver queue.
- break
- # If something went wrong, give back the jobs.
- if self.jobs:
- os.write(self.writer, self.jobs)
- raise e
-
- # Add a bump for our caller's reserveration, since we're just going
- # to sit here blocked on our child.
- self.claim = len(self.jobs) + 1
-
- except (KeyError, IndexError, ValueError, OSError, IOError):
- # Any missing environment strings or bad fds should result in just
- # not being parallel.
- self.claim = None
-
- self.is_open = True
-
- def close(self):
- """Return all reserved slots to Jobserver"""
-
- if not self.is_open:
- return
-
- # Return all the reserved slots.
- if len(self.jobs):
- os.write(self.writer, self.jobs)
-
- self.is_open = False
-
- def __enter__(self):
- self.open()
- return self
-
- def __exit__(self, exc_type, exc_value, exc_traceback):
- self.close()
-
- def run(self, cmd):
- """
- Run a command setting PARALLELISM env variable to the number of
- available job slots (claim) + 1, e.g. it will reserve claim slots
- to do the actual build work, plus one to monitor its children.
- """
- self.open() # Ensure that self.claim is set
-
- # We can only claim parallelism if there was a jobserver (i.e. a
- # top-level "-jN" argument) and there were no other failures. Otherwise
- # leave out the environment variable and let the child figure out what
- # is best.
- if self.claim:
- os.environ["PARALLELISM"] = str(self.claim)
-
- return subprocess.call(cmd)
+"""
+Determines how many parallel tasks "make" is expecting, as it is
+not exposed via an special variables, reserves them all, runs a subprocess
+with PARALLELISM environment variable set, and releases the jobs back again.

+See:
+ https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
+"""

def main():
"""Main program"""
diff --git a/scripts/lib/jobserver.py b/scripts/lib/jobserver.py
new file mode 100755
index 000000000000..a24f30ef4fa8
--- /dev/null
+++ b/scripts/lib/jobserver.py
@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0+
+#
+# pylint: disable=C0103,C0209
+#
+#
+
+"""
+Interacts with the POSIX jobserver during the Kernel build time.
+
+A "normal" jobserver task, like the one initiated by a make subrocess would do:
+
+ - open read/write file descriptors to communicate with the job server;
+ - ask for one slot by calling:
+ claim = os.read(reader, 1)
+ - when the job finshes, call:
+ os.write(writer, b"+") # os.write(writer, claim)
+
+Here, the goal is different: This script aims to get the remaining number
+of slots available, using all of them to run a command which handle tasks in
+parallel. To to that, it has a loop that ends only after there are no
+slots left. It then increments the number by one, in order to allow a
+call equivalent to make -j$((claim+1)), e.g. having a parent make creating
+$claim child to do the actual work.
+
+The end goal here is to keep the total number of build tasks under the
+limit established by the initial make -j$n_proc call.
+
+See:
+ https://www.gnu.org/software/make/manual/html_node/POSIX-Jobserver.html#POSIX-Jobserver
+"""
+
+import errno
+import os
+import subprocess
+import sys
+
+class JobserverExec:
+ """
+ Claim all slots from make using POSIX Jobserver.
+
+ The main methods here are:
+ - open(): reserves all slots;
+ - close(): method returns all used slots back to make;
+ - run(): executes a command setting PARALLELISM=<available slots jobs + 1>
+ """
+
+ def __init__(self):
+ """Initialize internal vars"""
+ self.claim = 0
+ self.jobs = b""
+ self.reader = None
+ self.writer = None
+ self.is_open = False
+
+ def open(self):
+ """Reserve all available slots to be claimed later on"""
+
+ if self.is_open:
+ return
+
+ try:
+ # Fetch the make environment options.
+ flags = os.environ["MAKEFLAGS"]
+ # Look for "--jobserver=R,W"
+ # Note that GNU Make has used --jobserver-fds and --jobserver-auth
+ # so this handles all of them.
+ opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
+
+ # Parse out R,W file descriptor numbers and set them nonblocking.
+ # If the MAKEFLAGS variable contains multiple instances of the
+ # --jobserver-auth= option, the last one is relevant.
+ fds = opts[-1].split("=", 1)[1]
+
+ # Starting with GNU Make 4.4, named pipes are used for reader
+ # and writer.
+ # Example argument: --jobserver-auth=fifo:/tmp/GMfifo8134
+ _, _, path = fds.partition("fifo:")
+
+ if path:
+ self.reader = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
+ self.writer = os.open(path, os.O_WRONLY)
+ else:
+ self.reader, self.writer = [int(x) for x in fds.split(",", 1)]
+ # Open a private copy of reader to avoid setting nonblocking
+ # on an unexpecting process with the same reader fd.
+ self.reader = os.open("/proc/self/fd/%d" % (self.reader),
+ os.O_RDONLY | os.O_NONBLOCK)
+
+ # Read out as many jobserver slots as possible
+ while True:
+ try:
+ slot = os.read(self.reader, 8)
+ self.jobs += slot
+ except (OSError, IOError) as e:
+ if e.errno == errno.EWOULDBLOCK:
+ # Stop at the end of the jobserver queue.
+ break
+ # If something went wrong, give back the jobs.
+ if self.jobs:
+ os.write(self.writer, self.jobs)
+ raise e
+
+ # Add a bump for our caller's reserveration, since we're just going
+ # to sit here blocked on our child.
+ self.claim = len(self.jobs) + 1
+
+ except (KeyError, IndexError, ValueError, OSError, IOError):
+ # Any missing environment strings or bad fds should result in just
+ # not being parallel.
+ self.claim = None
+
+ self.is_open = True
+
+ def close(self):
+ """Return all reserved slots to Jobserver"""
+
+ if not self.is_open:
+ return
+
+ # Return all the reserved slots.
+ if len(self.jobs):
+ os.write(self.writer, self.jobs)
+
+ self.is_open = False
+
+ def __enter__(self):
+ self.open()
+ return self
+
+ def __exit__(self, exc_type, exc_value, exc_traceback):
+ self.close()
+
+ def run(self, cmd, *args, **pwargs):
+ """
+ Run a command setting PARALLELISM env variable to the number of
+ available job slots (claim) + 1, e.g. it will reserve claim slots
+ to do the actual build work, plus one to monitor its children.
+ """
+ self.open() # Ensure that self.claim is set
+
+ # We can only claim parallelism if there was a jobserver (i.e. a
+ # top-level "-jN" argument) and there were no other failures. Otherwise
+ # leave out the environment variable and let the child figure out what
+ # is best.
+ if self.claim:
+ os.environ["PARALLELISM"] = str(self.claim)
+
+ return subprocess.call(cmd, *args, **pwargs)
--
2.51.0